Re: [ATM] Tracking Systems for Astrophotography

["Don Clement" <clement.focuser@verizon.net>]

>
> I use LMC6001, regarding the input bias, so I'm OK here.
>
> If you have a look at the sensors from a TV, stereo, etc, you will
> note that this same task is accomplished without most of these often
> expensive safeguards you refer to. I use air wiring, etc, but note
> that my circuits never come out as sensitive as the cheap one in my
> cheap TV that lacks all this. If you have some thoughts on how
> this is done, I think there would be a few people on this list and maybe
> sci.electronics.basics that would be quite interested.

I believe that the TV control sensors are working in IR, where silicon is
most sensitive, and detecting a modulated very strong signal from an IR LED.
Bob May's suggestion of a mechanical chopper is front of the quad detector
is good. A chopper is modulating the signal. One could use a synchronous
detector circuit or heterodyne type circuit  (thanks Edwin Armstrong) to
limit the BW (i.e. noise) and achieve very high gain with a modulated or
chopped signal.

BTW, I do build using the "dead bug" technique with flying air leads. Also
3M copper tape makes for an instant ground plane and can be soldered to.
Double sided tape and hot melt glue are great ways to mount ones electronic
entomology specimens (like the LMC6001AIH arachnid) on the copper tape...The
Gill Grissom method.  I just happen to have Teflon standoffs and T08 Teflon
sockets that worked for the low leakage I to E  circuit. YMMV



Don Clement

Running Springs, California

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